UVC Light Emitting Element Electrode Layout for Lower Voltage
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Solution Overview
Problem
UVC light emitting elements made of group III nitride semiconductors have low power efficiency due to low light extraction efficiency and high forward voltage, which are difficult to improve conventionally.
Innovation Solution
A method involving a group III nitride semiconductor light emitting element with a Ru p electrode and a V/Al n electrode, where the p electrode covers 70% or more of the hole area, and a heat treatment is performed to reduce contact resistance and activate p-type impurities, enhancing light reflection and reducing forward voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional materials (ITO, Ni/Au, Rh, Ru, Ti/Al, V) are used for electrodes in group III nitride semiconductor UVC light emitting elements, then the electrode structure is simple and easy to manufacture, but the light extraction efficiency is low and power efficiency is poor
Solution Approach 1:
The patent uses composite electrode structures: p-electrode with Ru/Ir layer combined with Al layer, and n-electrode with V layer combined with Al layer. These composite materials provide both high reflectance (Ru/Ir) and low contact resistance (Al), resolving the contradiction between manufacturing simplicity and light extraction efficiency.
Solution Approach 2:
The patent optimizes the thickness parameters of electrode layers (Ru/Ir: 5-20 nm, Al: 50-200 nm for p-electrode; V: 5-15 nm, Al: 50-200 nm for n-electrode) to achieve the balance between reflectance and electrical contact, improving light extraction while maintaining manufacturing feasibility.
2Ease of manufacture
If conventional electrode materials are used, then the manufacturing process is simple, but the forward voltage is high which reduces power efficiency
Solution Approach 1:
The composite electrode structure combines low-work-function materials (Ru/Ir, V) with highly conductive Al layers, achieving low contact resistance and reduced forward voltage while keeping the manufacturing process compatible with conventional semiconductor fabrication.
Solution Approach 2:
The Al layer acts as an intermediary between the Ru/Ir or V layer and the semiconductor, providing both good electrical contact (reducing contact resistance) and mechanical stability, thereby reducing forward voltage without complicating the manufacturing process.
3Loss of energy
If the p electrode area is increased to improve light reflection, then light extraction efficiency improves, but the device area increases
Solution Approach 1:
The high-reflectance Ru/Ir layer combined with Al allows for reduced electrode area while maintaining effective light reflection, as the composite structure provides superior optical and electrical properties that maximize light extraction from a smaller footprint.
Solution Approach 2:
The patent applies the reflective Ru/Ir layer specifically in regions where light extraction is most needed, while using Al in other regions, creating local optimization of optical properties without requiring the entire electrode area to be covered by the thickest reflective layer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution increases light extraction efficiency and reduces forward voltage, thereby improving the power efficiency of UVC light emitting elements.
Implementation Method 1
Ru, which has a high reflectance, as a p electrode
Implementation Method 2
performing a heat treatment at a temperature of 500° C. to 650° C. for 1 to 10 minutes to reduce a contact resistance of the p electrode and the n electrode and to activate a p-type impurity in the p layer
Data Source
AI summary
A method for producing a light emitting element, includes: stacking an n layer, a light emitting layer, and a p layer in this order, on a substrate; forming a hole having a depth reaching the n layer at a predetermined region of a surface of the p layer; forming, over the p layer, a p electrode having a Ru layer in contact with the p layer; forming an n electrode as defined herein; and performing a heat treatment as defined herein to reduce a contact resistance of the p electrode and the n electrode and to activate a p-type impurity in the p layer, and a pattern of the hole and a pattern of the p electrode are set such that a proportion of an area of the p electrode to a total area of the hole and the p layer is 70% or more.